Derivative Financial Instruments - Offsetting of Derivative Assets - Derivative Liabilities, Financial Liabilities, and Collateral Held by Counterparty (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	$ 3,790,649	$ 4,164,010
Financial instruments	(3,769,495)	(4,141,680)
Net amount of liabilities in the consolidated balance sheet	21,154	22,330
Credit Suisse First Boston Mortgage Capital LLC
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	1,690,452	1,235,430
Financial instruments	(1,685,301)	(1,235,430)
Net amount of liabilities in the consolidated balance sheet	5,151
Bank of America, N.A.
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	721,185	379,400
Financial instruments	(714,042)	(374,190)
Net amount of liabilities in the consolidated balance sheet	7,143	5,210
JP Morgan
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	108,195	936,172
Financial instruments	(108,195)	(936,172)
Morgan Stanley Bank
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	368,513	582,941
Financial instruments	(368,513)	(582,941)
BNP Paribas
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	193,740	183,880
Financial instruments	(193,740)	(183,880)
Royal Bank of Canada
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	360,389	175,897
Financial instruments	(360,389)	(175,897)
Citibank, N.A.
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	339,315	655,831
Financial instruments	(339,315)	(653,170)
Net amount of liabilities in the consolidated balance sheet		2,661
Wells Fargo Bank, N.A.
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet		11,212
Net amount of liabilities in the consolidated balance sheet		11,212
Federal National Mortgage Association
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	6,183
Net amount of liabilities in the consolidated balance sheet	6,183
Other
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	1,286	1,386
Net amount of liabilities in the consolidated balance sheet	1,286	1,386
Interest rate lock commitments
Derivative liabilities:
Net amounts of liabilities presented in the consolidated balance sheet	1,391	1,861
Net amount of liabilities in the consolidated balance sheet	$ 1,391	$ 1,861